Bounty bags now properly ignore Difficulty setting when opened. You can no longer get Imperial Gems or increased gold by opening them on a higher difficulty.*

Nevalistis précise même ceci sur le forum officiel:

Difficulty level has no impact on Horadric Cache loot. We recently hotfixed an issue where gems from Caches were erroneously being impacted by difficulty level, but this was not intended.

There are, however, special Legendaries that only drop from Horadric Caches. The Ring of Royal Grandeur, which reduces the number of items you need to complete a Set bonus by 1 to a minimum of 2, is such an example.